Abstract

A
longitudinal observational study on calf health and growth was conducted in
smallholder dairy farms in Mvomero and Njombe districts, Tanzania to investigate
whether calf growth in these regions was predominantly affected by clinical
diseases or other factors. The clinical health and growth of 156 calves from 121
farms were monitored for one year. Routine clinical examinations and bodyweight
measurements were conducted by the same veterinarian at each of four visits to
the study farms. Blood and faecal samples collected at each visit were screened
for haemoparasites and gastrointestinal parasites.

Calf mortality was 7.7 % and clinical signs of disease were
observed in 5.7 %. Coccidial oocysts and nematode eggs were detected in 24.8 %
and 14.8 % of 496 faecal samples, respectively, and haemoparasites in 16.9 %
(n=498). Mortality, together with nematode and coccidial infections, were
significantly associated with district and month of study. Bodyweight gain per
week ranged from -2.2 – 7.2 kg (mean 2.1, SD 1.5) in female calves and -1.8- 8
kg (mean 2.3, SD 1.5) in male calves. An extended period of impaired bodyweight
gain from birth to weaning was observed. Mean body condition score was 1.8.
Although the overall prevalence of clinical disease was low, calf growth rate
was impaired. Inadequate feeding was considered the major factor for this
observation and therefore it is recommended that calves are provided with
nutritionally appropriate feed in order to attain adequate growth performance.

Key words: Body weight gain, body condition score, diseases

Introduction

Sustainability of a dairy production system depends on good herd management.
Calf rearing is essential as it represents future replacement stock. Calf
diseases have been reported to be among the major constraints for dairy
production and expansion (Gitau et al 1994; Ehui et al 1995). The economic
impact of diseases could be direct (deaths), or indirect, through decreased
productivity and increased treatment expenses. The major causes of death in
dairy calves in Tanzania and other parts of Africa have been reported to be
various diseases including gastroenteritis due to coccidiosis, salmonellosis,
helminthiases and cryptosporidiosis, tickborne diseases (East Coast fever,
babesiosis, anaplasmosis and heartwater disease), and trypanosomosis (Chibunda
et al 1997; Keyyu et al 2005; Swai et al 2007; Kivaria and Noordhuizen 2009;
Nonga and Kambarage 2009).

Appropriate nutrition is fundamental for calf growth, and for the general
profitability of calf rearing enterprises (Lanyasunya et al 2006). In Tanzania,
where calf feeding regimes depend primarily on tropical grasses, it is difficult
for calves to obtain a balanced nutrient supply, as most of the available
natural forage has low digestibility due to relatively late harvesting during
maturation, and low crude protein and mineral content (Mero and Uden 1998;
Mtengeti et al 2008). In pre-weaned dairy calves, solid feed intake, especially
of a high carbohydrate diet, stimulates rumen microbial proliferation and
volatile fatty acid production. This enhances initiation of rumen development
(Baldwin et al 2004; Kehoe et al 2007), which, in turn, facilitates growth (Lanyasunya
et al 2006).

Analysis of growth patterns is useful for determining the relative importance of
factors that may affect production efficiency. Under normal circumstances, calf
growth has been shown to be elevated during the first weeks of life, and then
decline around weaning (Menchaca et al 1996; Bar-Peled et al 1997). Body
condition score (BCS) is a subjective measure of nutrient reserve, and changes
in calf BCS can be used as a practical indicator of nutritional status (Waltner
et al 1993).

Calves in most
smallholder dairy farms in Tanzania do not perform well, and most farmers have
limited knowledge on proper calf feeding regimens (Chang’a et al 2010). As few
studies on calf health and growth in smallholder farms in Tanzania have been
published, the objective of this study was to evaluate the health status and
growth of the young calves in smallholder dairy farms. By identifying those
factors that have the most impact on calf health and growth, preventive measures
could be implemented that have the most effective cost benefit for the farmers.

Materials and methods

Study area

The study was
conducted in 13 villages in the districts of Mvomero in Southeastern Tanzania,
and Njombe in the Southern Highlands of Tanzania. Further details of the study
sites have been published (Chang’a et al 2010).

Animals

The study
involved an open population. At the beginning/first visit, we started with 123
calves of day one to five months of age. New born calves were entered in the
subsequent visits given total of 156 calves from 121 smallholder dairy farms, 72
from Mvomero and 84 from Njombe. The calves were crossbred Friesian or Ayrshire
and Tanzanian Short Horn Zebu, and up to 57 weeks of age. Farms were visited by
the study veterinarian every two months, with a total of four visits to each
farm. All animals were ear tagged when first included in the study.

Calf examination

At each visit,
the body weights (BW) of the calves were estimated using a heart girth measuring
tape. The variable
BW gain was obtained as the difference in BW between
two consecutive visits. BCS for each calf was derived according to the
method described by Wildman et al (1982), which consists of a 1-5 scale, with
0.5 point increments. Date of birth, sex and the use of gastrointestinal
parasites drugs as a control measures were recorded. The health status of the
animals was assessed by routine clinical examination at each visit and all
animals showing signs of impaired health were recorded, along with clinical
symptoms. In cases of calf death, the most probable cause was identified either
by the farmer or the study veterinarian.

Sample collection and examination

The
material consisted of 1-4 samples from each of 156 individual calves, some
calves were withdrawn from the study at some point due to death and trading
given a total of 496 samples. Faecal samples were collected from the rectum of
each calf using disposable gloves. These were stored in a cool box with ice
packs during the 1-2 days transportation to the laboratory. Nematode egg and
coccidial oocyst concentrations were estimated using a modified McMaster
technique (Anonymous 1986). Briefly, 3 g of faeces were homogenized in 42 ml of
flotation fluid (saturated sodium chloride). The faecal suspension was passed
through a tea trainer to remove coarse material. After thorough mixing, two
chambers of a Universal McMaster slide were filled and all eggs and oocysts
under the grids (total volume 0.3 ml) counted at x40 magnification. The numbers
of eggs and oocysts counted were multiplied by 50 to provide an estimate of the
eggs/oocysts per gram (epg/opg) faeces.

Cryptosporidium
spp oocysts were detected using the modified Ziehl-Neelsen staining technique as
described by Henriksen and Pohlenz (1981). The suspected positive samples in Z-N
were retested using fluorescein-labeled (FITC) monoclonal antibody (A 100FR FL
from Waterborne Inc., New Orleans, USA) for conformation.

Blood was
collected from the jugular vein using heparinized tubes. Thin blood smears were
made, air-dried, fixed with absolute methanol, stained with 10% Giemsa solution
for 30 minutes, washed with tap water, air-dried and examined by microscopy at
x100 magnification for haemoparasites.

Statistical analysis

The statistical
software package, STATA 12 (Stata Corp LP, Texas) was used for the statistical
analyses. Differences in the prevalence of diseases, parasitic infections, and
calf mortality for each sex, season of birth, and district (Mvomero versus
Njombe) were compared by chi-square tests.

To assess the relationships between BW and age in weeks,
a
second order polynomial function was used as the
growth curve representation with the logarithmic transformed values of BW (kg)
as the outcome variable. The relationships between the two outcomes; BW
change and BCS, and the explanatory variable, calves’
age in days, were both represented by third order polynomial functions.
Repeat measures within calves were accounted for by
including calf ID as a random effects variable in all models. The
explanatory variables of sex, season of birth and district were initially
employed in all models, but omitted for no significance using the backwards
elimination procedure.

Results

Disease prevalence and
mortality

Of
156 calves, only 9 (5.7%) were diagnosed as being clinically diseased at one or
more of four visits. Gastrointestinal disorders were found to be most frequent
(2.7%). Other disorders include pneumonia (0.6%), photosensitization (0.6%), eye
infection (0.6%), anaemia (0.6%), and recumbency of unknown cause (0.6%).
Haemoparasites were detected in 84 (16.9%) of the 498 blood samples.
Theileria spp (15.9%) were the most prevalent haemoparasite, followed by
Babesia spp (0.8%), and Trypanosoma spp (0.2%). None of these
infections were related to month (P=0.13) or district (P=0.95),
but there was borderline association (P=0.08) with age. Younger calves
were more likely to be infected. No association was detected between
haemoparasitic infection and clinical disease (P=1.0). Out of 84 samples
detected with haemoparasites, only two had clinical disease.

Table 1. Calf mortality in relation to months in 156 calves
on 121 smallholder dairy farms in two districts in Tanzania

Months

Number of calves dead

Percentage

August-October

7

58

November-January

3

25

February-May

2

17

Total

12

100

X2
= 5.433, P = 0.06 (for the difference between the months of study)

The concentrations of
helminth eggs and oocysts in the faecal samples was generally low with most
positive samples having less than 500 oocysts (61%) or eggs (86%) per gram. Of
the positive samples, only 11 (9%) had over 2000 oocysts per gram, and only 2
(3%) had over 2000 helminth eggs per gram. Coccidial oocysts
were detected in 24.8% of the 496 faecal samples analysed. The infection was
related to district (P=0.005), borderline to months (P=0.06), but
appeared not to be affected by calf age (P=1.0). More coccidian positive
samples were found in Mvomero than Njombe and most positive samples were
collected between August-October. No association between coccidial infection and
clinical disease in the calves could be identified (P=1.0). Out of 123
samples detected with coccidial oocysts, only one had clinical disease.
Gastrointestinal nematode eggs were detected in 14.8% of the 496 faecal samples
analysed. Infection with gastrointestinal nematodes was related to months (P=0.04)
and districts (P=0.003), but was not associated with age (P=0.99).
More nematode positive samples were found in Mvomero than Njombe, and most
positive samples were collected between August-October. Out of 74 samples
detected with nematode eggs, only one had clinical disease (P=1.0). Mixed
intestinal infection with both coccidia and nematodes was observed in 6.8% of
the samples. Most farmers treated their animals against gastrointestinal
parasites every third month.
Thirteen (2.6%) samples were suspected as Cryptosporidium
positives in Z-N staining; however, on confirmatory test none was found to be
positive.

A
total of 12 (7.7%) calves died during the study period, 8 (67%) from Mvomero and
4 (33 %) from Njombe (Table 1). The causes of death, as perceived by the
farmers, included one case of each of the following: East Coast fever,
anaplasmosis, diarrhoea, paralysis, sudden death, accident, and dog bite.
Furthermore, two calves died from pneumonia and three of unknown causes. Death
was related to district (P=0.045) and borderline related with months (P=0.06)
(Table 1).

Table 2.
The relationship between body weight gain and age in 156 calves of dairy
crossed breeds on 121 smallholder dairy farms in Tanzania expressed by a
third order polynomial function. Repeated measures within
calves were accounted for by including calf ID as a random effects
variable in STATA 12.

Weight change

Coefficient

SE

Z

P

Age wks

0.0288

7.48x10-3

3.85

0.00

Age-sq

-8.34x10-5

2.23x10-4

-0.38

0.707

Age-cub

-4.56x10-5

1.0x10-5

4.56

0.00

Constant

1.55

0.279

5.54

0.00

Table 3. The relationship between body condition score and age in
156 calves of dairy crossbreeds on 121 smallholder dairy farms in
Tanzania, as expressed by a third order polynomial function. Repeated measures within calves were accounted for by
including calf ID as a random effects variable in STATA 12.

Weight change

Coefficient

SE

Z

P

Age wks

4.59x10-3

1.84x10-3

2.50

0.012

Age-sq

2.13x10-4

5.1x10-5

4.17

0.000

Age-cub

-5.69x10-6

2.46x10-6

-2.31

0.021

Constant

1.59

0.0655

24.3

0.000

Body
weight

The
measures for weekly BW gain in heifer calves ranged from -2.2 to 7.2 kg (mean
2.1, SD 1.5), and from -1.8 to 8.1 kg (mean 2.3 kg, SD 1.6) in male calves
(Table 2). The third order polynomial model which shows the relationship between
BW gain and age is displayed in Table 2 and Figure 1. Median age at weaning was
16 weeks (mean 16.0 weeks, SD 3.7).

Figure 1. Weekly body weight gain by age in male (--■--) and
female (--▲--) calves (n = 156) on 121 smallholder dairy farms,
Tanzania. A third order polynomial function was observed. Adjustment for
repeated measures within calves was used in STATA 12

Body
condition score

The
relationship between BCS and age was found to be significant (P<0.005)
(Table 3, Figure 2). Body condition score decreased from 1.85 at birth to 1.75
at 25 weeks of age, and then rose with further animal maturation.

Figure 2.
Body condition score by age in male (--■--) and female (--▲--) calves
(n=156) on 121 smallholder dairy farms in Tanzania. A third order
polynomial function was observed. Adjustment for repeated measures
within calves was used in STATA 12

Discussion

The findings in
this study do not support the supposition that diseases are a primary cause for
growth retardation in crossbred calves at these study sites in Tanzania, as only
a small proportion of calves were diagnosed with clinical signs of disease
during the four herd visits. Although both haemoparasites and intestinal
parasites were diagnosed relatively frequently, their occurrence was not
apparently related to clinical disease. However both egg counts and coccidial
oocyst counts were relatively low and it is possible that non-pathogenic
coccidia predominated. The low gastrointestinal parasites counts could be
attributed to frequently use of parasite prophylactic drugs. Additionally,
cryptosporidiosis was found not to be a problem in these herds. Thus, the
sub-optimal growth rates appear to be due to a non-infectious, chronic problem.

We hypothesize
that inadequate feeding regimes, rather than diseases, probably had a greater
impact on calf growth. In this study, a long period of declining weekly BW gain
after birth to weaning was observed, which differs from the normal profile of BW
gain as described by Menchana et al (1996). This indicates problems related to
nutrition, specifically during the period of conversion from milk feeding to
rumination. Lyimo et al (2004) reported that most farmers in Tanzania introduce
forage as late as at the 4th week after birth, and provided little
supplement to their calves after weaning. Inadequate supplementation with solid
feed to calves that are growing rapidly during the pre-weaning period, results
in delayed ruminal development and growth (Khan et al 2007), and probably
contributes to a decline in body weight gain, as observed during this study.
During the weaning period, animals may display low or negative daily gain, and
the current study identifies this period as being particularly critical for
achieving optimum growth. If solid feed intake can be encouraged during the milk
feeding period, then it has been suggested that the decrease in growth rate
before and around weaning will be less severe (Forbes 1986). A similar pattern
of decline of daily BW gain from birth to weaning has previously been reported
by Das et al (1999) in Tanzania, supporting our suggestion that natural pasture
in this area of the tropics does not provide adequate nutrients for optimum
growth of calves.

High growth
rate during the post weaning period was expected, due to compensatory gain, a
phenomenon demonstrated by Choi et al (1997) in 6-month old Holstein heifers
subjected to a step-growth pattern. Greater nutrient demands, because of higher
BW and increased size of digestive organs, trigger hyperphagicity in calves
after weaning (Bøe and Havrevoll 1993). A point of maximum BW gain, as observed
around the age of 40 weeks, has also previously been described for the tropical
Brahman breed (Menchaca et al 1996), but the point of inflection was
considerably earlier than in the present investigation. This was possibly due to
a difference in the quality of feed available to the calves.

In
the tropics, reliance on low quality pasture grass alone does not result in good
rumen development in calves (Mbwile 1990), and this may have resulted in the
retarded calf growth observed in the current study. In Mvomero, most natural
grasses and crop residues have low crude protein and mineral content, and are of
poor digestibility (Mtengeti et al 2008) and thus do not reach the requirements
needed for optimum growth in the calves. Additionally, in this study area, as in
most rural areas in Tanzania, it is unusual to use concentrates for feeding
calves (Lyimo et al 2004) due to reasons of economy and erratic supply, and this
lack would also result in poor growth rates of the calves. Increases in calf BW
gain following improvements in nutritional regimen have been demonstrated by
several authors (Baldwin et al 2004; Lanyasunya et al 2006), and it is well
established that for optimum calf growth, good quality roughage should be
provided prior to weaning.

An
increase in mortality rate and the occurrence of intestinal parasites occurred
between August and October. This is the peak of the dry season in this area,
when the availability of animal feed, in terms of both quality and quantity, is
low (Mussa 1998). Inadequate feeding during this period, along with high ambient
temperature, may result in a reduction in nutritional status and decreased
resistance to disease (Radostits et al 1994).

The
higher mortality and parasite burden in Mvomero than Njombe were probably due to
differences in experience in rearing dairy cows (Urio et al 2006). Inhabitants
of Mvomero are traditionally crop growers with relatively little experience in
rearing dairy cows, while farmers in Njombe have a long tradition of keeping
dairy cows.

Conclusion

Growth
rates of calves on smallholder dairy farms in Tanzania were low. This seemed to
be related to inadequate nutrition rather than diseases. Additional management
options should be explored in this system with particular focus on improving
feed quality, especially in pre-weaning and weaning periods, as these seem to be
problematic stages. Treatment for helminths and coccidial infections might be
most strategically administered after the end of the rainy season as this period
showed the highest infestation rate.

Acknowledgements

The financial
support given by the Norwegian Government through the PANTIL project at Sokoine
University of Agriculture is gratefully acknowledged. We also acknowledge the
cooperation from dairy farmers participating in the study and field officers in
Mvomero and Njombe districts.

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